1. Energy: Forms and Changes
Chapter 9
Energy: Forms and Changes
Section 3: Conservation of Energy

2. Essential Questions How is energy conserved in a closed system?
What is the law of conservation of energy?
What are some examples of how thermal energy is always a result of energy conversion?
Why is perpetual motion impossible?

3. The Law of Conservation of Energy
Energy can be neither created nor destroyed by ordinary means.
It can only be converted from one form to another.
If energy seems to disappear, then scientists look for it – leading to many important discoveries.

4. Where Does the Energy Go?
Energy can not be lost.
Roller coaster example: Some of the potential and kinetic energy is released as thermal energy because of FRICTION

5. A Closed System
A closed system – a group of objects that transfer energy only to each other
If all types of energy are added up, you can see none is lost, just changed

6. Law of Conservation of Energy
Energy cannot be created or destroyed.
The total amount of energy in a closed system is always the same.
Any number of conversions could take place, though.

7. Thermal Energy
Any time an energy conversion takes place, some is converted to thermal energy. This is why there is no such thing as perpetual motion.
This thermal energy is due to FRICTION.

8. Energy Efficiency
Energy efficiency is a comparison before and after conversion
Energy conversions that waste less energy are efficient
Aerodynamic cars are an example